Digitrax Decoders Inst in MT SW1500 & ATL MP15DC & Nothing Happening

[peteski]

Russ, to me it didn't seem like you were bashing any product - you simply had some problems and were reaching out for some assistance.

Even if you get the decoder replaced, the problem might still be there when you install the new decoder.  But I have no way of knowing that. I never installed the SW-1500 decoder - my knowledge is based on general DCC/electronic knowledge and on what I have seen about the decoder in online forums. Like Philip said, maybe there is some piece of insulating tape missing which is supposed to prevent it from shorting out to the loco's frame (even thought the installation manual doesn't mention anything about that). Or the decoder was defective from the start (but then the smoke you saw seem to point in another direction).

[Philip H]

And I apologize profusely for how hard autocorrect makes it to read my posts.

As a rule when I'm doing my own installs I run Kapton tape between the decode and any part of the frame it's Not supposed to touch. Saves a ton of trouble.

[tehachapifan]

Thanks Peteski and Phillip. I appreciate the help!

Well, after taking some time away from the layout, I decided to tear apart the loco and see if I could identify and potential short spot and may have found one (maybe two?). It looks like a tiny hole had developed in the insulation tape between the motor and the frame, where I believe the motor lead attaches to the motor on that side. It also appeared that the motor casing itself might have been in contact with the frame too, but I'm not sure if that is a potential short or not(?). I put some Kapton tape over the hole and where the motor casing was possibly contacting the frame, reassembled everything and tried again with my fingers crossed. Still nothing but agree the decoder was probably already rendered inoperable.

...forgot to mention, I did put some Kapton tape on the frame under the decoder when I first installed it. The decoder components do sit VERY close to the frame.

[crappie]

 did you program it ?

[Philip H]

That exposed wire  sounds like your culprit.

[Rich Businger]

The second run if these locomotives have a motor contact shorted to the frame.  You need to make sure the motor is 100% isolated.  MTL is aware of this problem.


Rich

[peteski]

The second run if these locomotives have a motor contact shorted to the frame.  You need to make sure the motor is 100% isolated.  MTL is aware of this problem.


Rich

Now he tells us.... 

Seriously, it is good to know - hopefully the word will get out so others don't fry their decoders. Kind of reminds me of the initial problem with Kato GS-4.